Roger Federer and Novak Djokovic and Simona Halep and Angelique Kerber continue their quests for potential semifinal matchups when fourth-round matches conclude in their halves of the draw at Melbourne Park. Defending champion Federer plays former top-ranked junior Marton Fucsovics, who upset 13th-seeded Sam Querrey in the second round. Djokovic, a six-time champion here, plays Hyeon Chung, who provided one of the big upsets of the tournament when he beat fourth-seeded Alexander Zverev. Djokovic and Chung have met only once, when Djokovic beat him in straight sets in the first round at Melbourne Park two years ago. "I'm just happy to share the court with Novak," said 21-year-old Chung. Federer and Djokovic could only meet in the semifinals.

Halep and Kerber also head towards a potential semifinal meeting, and Kerber has form on her side. She's on a 12-match winning streak, including the Sydney International title and a third-round win here over Maria Sharapova. Top-seeded Halep barely scraped through her third-round match, needing 3 hours and 45 minutes and a 15-13 scoreline in the deciding set to beat Lauren Davis. Halep, who has a left ankle injury, plays Naomi Osaka, who beat local favorite Ash Barty in the third round. "Osaka is hitting strong, so strong," Halep says. "I have to be strong, if I can, on my legs, and just stay there, playing fast, opening the court, as I do all the time."

Kerber, the 2016 champion here, plays Hsieh Su-wei of Taiwan. Hsieh, who plays with an unusual two-handed grip and is coached by former Australian doubles specialist Paul McNamee, beat Wimbledon champion Garbine Muguruza and 26th-seeded Agnieszka Radwanska in earlier rounds.

__ By AP Sports Writer Dennis Passa.

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MONDAY FORECAST

Mostly sunny, high of 25 Celsius (77 Fahrenheit)

SUNDAY'S WEATHER

Mostly sunny, high of 28 C (82 F)

ATTENDANCE

First-week attendance was 505,443, exceeding a half-million spectators over the first seven days for only the second time.